Methods exist for reducing background noise in an adverse audio environment. One such method is to use a stationary noise suppression system. The stationary noise suppression system will always provide an output noise that is a fixed amount lower than the input noise. Typically, the stationary noise suppression is in the range of 12-13 decibels (dB). The noise suppression is fixed to this conservative level in order to avoid producing speech distortion, which will be apparent with higher noise suppression.
Some prior art systems invoke a generalized side-lobe canceller. The generalized side-lobe canceller is used to identify desired signals and interfering signals comprised by a received signal. The desired signals propagate from a desired location and the interfering signals propagate from other locations. The interfering signals are subtracted from the received signal with the intention of cancelling interference.
Previous audio devices have incorporated two microphone systems to reduce noise in an audio signal. A two microphone system can be used to achieve noise cancellation or source localization, but is not suitable for obtaining both. With two widely spaced microphones, it is possible to derive level difference cues for source localization and multiplicative noise suppression. However, with two widely spaced microphones, noise cancellation is limited to dry point sources given the lower coherence of the microphone signals. The two microphones can be closely spaced for improved noise cancellation due to higher coherence between the microphone signals. However, decreasing the spacing results in level cues which are too weak to be reliable for localization.